<article id="wikiArticle">
<div></div>
<p>可枚举属性是指那些内部 “可枚举” 标志设置为 true 的属性，对于通过直接的赋值和属性初始化的属性，该标识值默认为即为 true，对于通过 <a href="Reference/Global_Objects/Object/defineProperty">Object.defineProperty</a> 等定义的属性，该标识值默认为 false。可枚举的属性可以通过 <a href="Reference/Statements/for...in">for...in</a> 循环进行遍历（除非该属性名是一个 <a href="Reference/Global_Objects/Symbol">Symbol</a>）。属性的所有权是通过判断该属性是否直接属于某个对象决定的，而不是通过原型链继承的。一个对象的所有的属性可以一次性的获取到。有一些内置的方法可以用于判断、迭代/枚举以及获取对象的一个或一组属性，下表对这些方法进行了列举。对于部分不可用的类别，下方的示例代码对获取方法进行了演示。</p>
<div style="overflow: auto; width: 100%;">
<table>
<caption>属性的可枚举性和所有权 - 内置的判断、访问和迭代方法</caption>
<tbody>
<tr>
<th>功能</th>
<th>自身对象</th>
<th>自身对象及其原型链</th>
<th>仅原型链</th>
</tr>
<tr>
<td>判断</td>
<td>
<table>
<thead>
<tr>
<th scope="col">可枚举属性</th>
<th scope="col">不可枚举属性</th>
<th scope="col">可枚举属性及不可枚举属性</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty">hasOwnProperty</a></code></p>
</td>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty">hasOwnProperty</a></code> – filtered to exclude enumerables using <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code></p>
</td>
<td><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty">hasOwnProperty</a></code></td>
</tr>
</tbody>
</table>
</td>
<td>
<table>
<thead>
<tr>
<th scope="col">可枚举属性</th>
<th scope="col">不可枚举属性</th>
<th scope="col">可枚举属性及不可枚举属性</th>
</tr>
</thead>
<tbody>
<tr>
<td>需要额外代码实现</td>
<td>需要额外代码实现</td>
<td><code><a href="/en-US/docs/Web/JavaScript/Reference/Operators/in">in</a></code></td>
</tr>
</tbody>
</table>
</td>
<td>需要额外代码实现</td>
</tr>
<tr>
<td>访问</td>
<td>
<table>
<thead>
<tr>
<th scope="col">可枚举属性</th>
<th scope="col">不可枚举属性</th>
<th scope="col">可枚举属性及不可枚举属性</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys">Object.keys</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></p>
</td>
<td><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code>, <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a> </code>– filtered to exclude enumerables using <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code></td>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></p>
</td>
</tr>
</tbody>
</table>
</td>
<td>需要额外代码实现</td>
<td>需要额外代码实现</td>
</tr>
<tr>
<td>迭代</td>
<td>
<table>
<thead>
<tr>
<th scope="col">可枚举属性</th>
<th scope="col">不可枚举属性</th>
<th scope="col">可枚举属性及不可枚举属性</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys">Object.keys</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></p>
</td>
<td><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code>, <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code> – filtered to exclude enumerables using <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code></td>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code></p>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></p>
</td>
</tr>
</tbody>
</table>
</td>
<td>
<table>
<thead>
<tr>
<th scope="col">可枚举属性</th>
<th scope="col">不可枚举属性</th>
<th scope="col">可枚举属性及不可枚举属性</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<p><code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/for...in">for..in</a></code></p>
<p>(excluding symbols)</p>
</td>
<td>需要额外代码实现</td>
<td>需要额外代码实现</td>
</tr>
</tbody>
</table>
</td>
<td>需要额外代码实现</td>
</tr>
</tbody>
</table>
</div>
<h2 id="通过可枚举性和所有权获取对象的属性">通过可枚举性和所有权获取对象的属性</h2>
<p>注：以下实现并非使用于所有情况的最优算法，但可以快捷的展示语言特性。</p>
<ul>
<li>使用 <code>SimplePropertyRetriever.theGetMethodYouWant(obj).indexOf(prop) &gt; -1</code> 时将发生判断操作。</li>
<li>使用 <code>SimplePropertyRetriever.theGetMethodYouWant(obj).forEach(function (value, prop) {});</code> 时将发生迭代操作。 (或使用 <code>filter()</code>、<code>map()</code> 等方法)</li>
</ul>
<pre><code  class="language-javascript">var SimplePropertyRetriever = {
    getOwnEnumerables: function(obj) {
        return this._getPropertyNames(obj, true, false, this._enumerable); 
         // Or could use for..in filtered with hasOwnProperty or just this: return Object.keys(obj);
    },
    getOwnNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, false, this._notEnumerable);
    },
    getOwnEnumerablesAndNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, false, this._enumerableAndNotEnumerable); 
        // Or just use: return Object.getOwnPropertyNames(obj);
    },
    getPrototypeEnumerables: function(obj) {
        return this._getPropertyNames(obj, false, true, this._enumerable);
    },
    getPrototypeNonenumerables: function(obj) {
        return this._getPropertyNames(obj, false, true, this._notEnumerable);
    },
    getPrototypeEnumerablesAndNonenumerables: function(obj) {
        return this._getPropertyNames(obj, false, true, this._enumerableAndNotEnumerable);
    },
    getOwnAndPrototypeEnumerables: function(obj) {
        return this._getPropertyNames(obj, true, true, this._enumerable); 
        // Or could use unfiltered for..in
    },
    getOwnAndPrototypeNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, true, this._notEnumerable);
    },
    getOwnAndPrototypeEnumerablesAndNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, true, this._enumerableAndNotEnumerable);
    },
    // Private static property checker callbacks
    _enumerable: function(obj, prop) {
        return obj.propertyIsEnumerable(prop);
    },
    _notEnumerable: function(obj, prop) {
        return !obj.propertyIsEnumerable(prop);
    },
    _enumerableAndNotEnumerable: function(obj, prop) {
        return true;
    },
    // Inspired by http://stackoverflow.com/a/8024294/271577
    _getPropertyNames: function getAllPropertyNames(obj, iterateSelfBool, iteratePrototypeBool, includePropCb) {
        var props = [];

        do {
            if (iterateSelfBool) {
                Object.getOwnPropertyNames(obj).forEach(function(prop) {
                    if (props.indexOf(prop) === -1 &amp;&amp; includePropCb(obj, prop)) {
                        props.push(prop);
                    }
                });
            }
            if (!iteratePrototypeBool) {
                break;
            }
            iterateSelfBool = true;
        } while (obj = Object.getPrototypeOf(obj));

        return props;
    }
};</code></pre>
<h2 id="统计表">统计表</h2>
<div style="width: 100%; overflow: auto;">
<table>
<thead>
<tr>
<th scope="row"> </th>
<th scope="col"><code>in</code></th>
<th scope="col"><code>for..in</code></th>
<th scope="col"><code>obj.hasOwnProperty</code></th>
<th scope="col"><code>obj.propertyIsEnumerable</code></th>
<th scope="col"><code>Object.keys</code></th>
<th scope="col"><code>Object.getOwnPropertyNames</code></th>
<th scope="col"><code>Object.getOwnPropertyDescriptors</code></th>
<th scope="col"><code>Reflect.ownKeys()</code></th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">可枚举自身属性</th>
<td>true</td>
<td>true</td>
<td>true</td>
<td>true</td>
<td>true</td>
<td>true</td>
<td>true</td>
<td>true</td>
</tr>
<tr>
<th scope="row">不可枚举自身属性</th>
<td>true</td>
<td>false</td>
<td>true</td>
<td>false</td>
<td>false</td>
<td>true</td>
<td>true</td>
<td>true</td>
</tr>
<tr>
<th scope="row">Symbols keys</th>
<td>true</td>
<td>false</td>
<td>true</td>
<td>true</td>
<td>false</td>
<td>false</td>
<td>true</td>
<td>true</td>
</tr>
<tr>
<th scope="row">可枚举继承属性</th>
<td>true</td>
<td>true</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
</tr>
<tr>
<th scope="row">不可枚举继承属性</th>
<td>true</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
</tr>
<tr>
<th scope="row">Inherited Symbols keys</th>
<td>true</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
<td>false</td>
</tr>
</tbody>
</table>
</div>
<h2 id="参见">参见</h2>
<ul>
<li><code><a href="Reference/Operators/in">in</a></code></li>
<li><code><a href="Reference/Statements/for...in">for..in</a></code></li>
<li><a href="Reference/Global_Objects/Object/hasOwnProperty" title="hasOwnProperty() 方法会返回一个布尔值，指示对象自身属性中是否具有指定的属性"><code>Object.hasOwnProperty()</code></a></li>
<li><a href="Reference/Global_Objects/Object/propertyIsEnumerable" title="propertyIsEnumerable() 方法返回一个布尔值，表示指定的属性是否可枚举。"><code>Object.propertyIsEnumerable()</code></a></li>
<li><a href="Reference/Global_Objects/Object/getOwnPropertyNames" title="Object.getOwnPropertyNames()方法返回一个由指定对象的所有自身属性的属性名（包括不可枚举属性但不包括Symbol值作为名称的属性）组成的数组。"><code>Object.getOwnPropertyNames()</code></a></li>
<li><a href="Reference/Global_Objects/Object/keys" title="Object.keys() 方法会返回一个由一个给定对象的自身可枚举属性组成的数组，数组中属性名的排列顺序和使用 for...in 循环遍历该对象时返回的顺序一致 。"><code>Object.keys()</code></a></li>
<li><a href="Reference/Global_Objects/Object/getOwnPropertyDescriptors" title="Object.getOwnPropertyDescriptors() 方法用来获取一个对象的所有自身属性的描述符。"><code>Object.getOwnPropertyDescriptors()</code></a></li>
</ul>
</article>